Dr. Molinda M. Chartrand of the Boston University School of Medicine and colleagues studied 169 families with children from 18 months to age 5 who were enrolled in military childcare centers at a large Marine base in 2007.

Parents and childcare providers each completed a behavior problem assessment that analyzed anxiousness, depression and withdrawal, as well as attention problems and aggression behaviors.

Parents also completed a questionnaire to measure their own level of depression.

The study, published in the Archives of Pediatrics & Adolescent Medicine, found that of the 169 families, 33 percent had a deployed parent, with an average deployment length of 3.9 months. Children age 3 and older who had a deployed parent had significantly higher scores on measures of externalizing and overall behavior problems than children of the same age without a deployed parent.

"Such reported differences might be dismissed as distorted perceptions of the child by the distressed non-deployed parent; however, the association remained after controlling for parental stress and depressive symptoms," the study authors said in a statement. "In addition, childcare providers reported similarly elevated scores."